Animal Luminescence 551 



amount of carbon dioxide is produced. Although the CO2 pro- 

 duced by the respiring tissue could not be separated from CO, 

 produced by the chemical reaction actually producing light, and 

 the conclusion may not be correct, the idea that light came from 

 the oxidation of an organic carbon compound was definitely modem. 

 To quote Matteucci's own words (1847: 182; : " In the luminous 

 segments of these animals, enveloped by transparent membranes, 

 and by means of the numerous tracheae discovered here and there 

 in these animals, atmospheric oxygen is brought in contact with a 

 substance, sui generis, principally composed of carbon, hydrogen, 

 oxygen, and azote." Thereby the light is produced. Knowledge 

 that a number of additional compounds are necessary for lijht pro- 

 duction in the firefly was to come in the twentieth centurv'. Mat- 

 teucci's work by no means concludes the nineteenth-century physio- 

 logical and chemical investigations of the Lampyridae, but will serve 

 as a convenient stopping place in anticipation of the modem period. 

 The many papers which filled in the details of lampyrid physiology 

 during the last half of the nineteenth century added little of im- 

 portance for our history'. 



PHYSICAL NATURE OF THE LIGHT 



Firefly and glowworm light is particularly well suited for physical 

 investigations, although perhaps not as bright or as easy to study 

 as that of the cucujo, Pyrophorus, discussed in a later section. The 

 early attempts to detect heat from glo^vworms all failed, and even 

 modern measurements, like those of W. W. Coblent2 (1912) in 

 A Physical Study of the Fire-fly, have led to results difficult to 

 interpret. 



John Murray 0826) was probably the first to report on examina- 

 tion of the glo^s^sorm light with a prism, and to find that it " seems 

 monochromatic and incapable of further decomposition." This 

 result was due to faulty conditions. Dr. Lehman /'1862> and J. 

 Schnauss fl862) both observed the presence of red, yellow, and 

 green components, and Schnauss noted that the light would affect 

 a photographic plate, making it similar to ordinar\- light, with no 

 unusual qualities, as some workers had supposed. Since 1862, C. A. 

 Young (1870), P. Secci (1872), H. A. Sevem (1881), J. Conroy 

 (1882), and J. Spiller (1882) have all found the spectra of 1am'- 

 pyrids to be short bands, entirely in the visible region but made up 

 of several colors. Spectral energy curves were first plotted in the 

 twentieth century-, as a result of the work of H. E. Ives and ^V. ^V. 

 Coblentz (1910)'. 



